Methods for the preparation, formulation and use of lithium valproate

ABSTRACT

The present invention relates to methods for preparing lithium valproate and administering this compound to a subject in need of treatment with lithium and/or valproate. Pharmaceutical compositions are also provided that are useful therapies for the treatment of neurological, immunological, and viral-mediated disorders in warm-blooded mammals.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of application Ser. No. 11/725,414 filed Mar. 19,2007, of the same title.

FIELD OF THE INVENTION

The present invention relates to methods for preparing lithiumvalproate, its pharmaceutical formulations, and administering thiscompound to a subject in need of treatment with lithium and/orvalproate. Pharmaceutical compositions are also provided that are usefultherapies for the treatment of neurological, immunological, andretroviral-mediated disorders in warm-blooded mammals.

BACKGROUND OF THE INVENTION

The National Institute of Neurological Disorders and Stroke sponsored arecent survey of twelve neurological disorders which confirms that theburden of neurologic illness affects many millions of people in theUnited States. [Hirtz D, Thurman D J, Gwinn-Hardy K, Mohamed M,Chaudhuri A R, Zalutsky R. How common are the “common” neurologicdisorders? Neurology 2007 Jan. 30; 68(5): 326-37.] The data indicatethat more than two million people in the U.S. (i.e., slightly more thanseven per 1,000) have epilepsy. Similarly, more than 35 millionindividuals live with migraines, a prevalence of 121 out of 1,000.

Likewise, bipolar disorder (BPD) is a prevalent and debilitatingmanic-depressive illness, affecting approximately 1% of the populationworldwide. BPD, a psychosis characterized by cyclic periods of mania anddepression, is associated with significant morbidity and mortality, withsuicide as a cause of death in as many as 10% of patients. Little isknown about the pathogenesis of BPD, but it responds remarkably well tomood-stabilizing drugs, such as lithium ion (lithium), and theanticonvulsant valproate.

Further, as many as 900,000 Americans are infected with the humanimmunodeficiency virus (HIV). Before the arrival of modern antiviraltherapies in the late 1990's, HIV effected rapidly devastating effectson the brain known as HIV-associated dementia (HAD) or neuroAlDS. Thecurrent, standard combination of HIV treatments (also known as highlyactive antiretroviral treatment or HAART) has extended the lives of mostU.S. AIDS patients, but has not cured neuroAlDS, despite early reportsto the contrary. Current antiviral combinations slow the onset ofHIV-related nerve damage that becomes more common the longer HIVpatients live. Therefore, whereas patients suffered rapid, severeneurological damage before HAART therapy, they now gradually loseattention span, memory, speaking ability and decision-making skillsdespite the best available treatment.

Clinical Uses

Valproic acid (valproate) has been approved by regulatory agenciesaround the world, including the U.S. Food and Drug Administration (FDA),as a therapy for several clinical indications, including neurologicaldisorders, mania, manic episodes associated with bipolar disorder,epilepsy, and affective and attention deficit disorders. In addition,valproate is used for the prophylactic treatment, modulation andmanagement of migraine headache, chronic pain, and neuropathic pain.

Although the underlying therapeutic mechanisms are unclear, a growingbody of evidence suggests that valproate has neuroprotective andneurotrophic actions. For example, both brain imaging and post-mortemstudies demonstrate that bipolar disorder involves a decrease in thevolume and number of neurons and glia in discrete brain areas thought tobe important for cognition and mood regulation. Remarkably, thereduction in brain volume in bipolar patients was found to be largelysuppressed by chronic treatment with valproate, in part as a consequenceof its histone deacetylase inhibition. [Kanai H, Saws A, Chen R W, LeedsP, Chuang D M. Valproic acid inhibits histone deacetylase activity andsuppresses excitotoxicity-induced GAPDH nuclear accumulation andapoptotic death in neurons. Pharmacogenom J 2004; 4: 336-344.] Likewise,in cellular models, valproate protects rat cerebral cortical neurons andcerebellar granule cells from glutamate-induced excitotoxicity andapoptotic death from stress on the endoplasmic reticulum in C6 gliomacells and PC12 cells. [Bown C D, Wang J F, Chen B, Young L T. Regulationof ER stress proteins by valproate: therapeutic implications. BipolarDisord 2002; 4: 145-151.] In a rat model of stroke, post-insultvalproate treatment reduces ischemia-induced brain damage, caspase-3activation and neurological deficits. [Ren M, Leng Y, Jeong M, Leeds PR, Chuang D M. Valproic acid reduces brain damage induced by transientfocal cerebral ischemia in rats: potential roles of histone deacetylaseinhibition and heat shock protein induction. J Neurochem 2004; 89:1358-1367.] A number of studies report that valproate activates cellsurvival factors such as Akt, extracellular signal-regulated proteinkinase, and cyclic AMP response element binding protein. [De Sarno P, LiX, Jope R S. Regulation of Akt and glycogen synthase kinase-3 betaphosphorylation by sodium valproate and lithium. Neuropharmacology 2002;43: 1158-1164. Yuan P X, Huang L D, Jiang Y M, Gutkind J S, Manji H K,Chen G. The mood stabilizer valproic acid activates mitogen-activatedprotein kinases and promotes neurite growth. J Biol Chem 2001; 276:31674-31683. Einat H, Yuan P, Gould T D, Li J, Du J, Zhang L, et al. Therole of the extracellular signal-regulated kinase signaling pathway inmood modulation. J Neurosci 2003; 23: 7311-7316.] Additionally,valproate induces cytoprotective proteins such as Bcl-2, Grp78,brain-derived neurotrophic factor, and heat-shock protein 70. [Chen G,Zeng W Z, Yuan P X, Huang L D, Jiang Y M, Zhao Z H et al. Themood-stabilizing agents lithium and valproate robustly increase thelevels of the neuroprotective protein bcl-2 in the CNS. J Neurochem1999; 72: 879-882.] Moreover, valproate promotes neurite outgrowth.[Yuan P X, Huang L D, Jiang Y M, Gutkind J S, Manji H K, Chen G. Themood stabilizer valproic acid activates mitogen-activated proteinkinases and promotes neurite growth. J Biol Chem 2001; 276:31674-31683.] Recently, valproate was shown to protect dopaminergicneurons in midbrain neuron/glia cultures by stimulating the release ofneurotrophic factors from astrocytes. [Chen P-S, Peng G-S, Li G, Yang S,Wu X, Wang C-C, Wilson B, Lu R-B, Gean P-W, Chuang D-M, Hong J-S.Valproate protects dopaminergic neurons in midbrain neuron/glia culturesby stimulating the release of neurotrophic factors from astrocytes.Molec Psych 2006; 11: 1116-1125.] Further, valproate at therapeuticlevels was reported to inhibit histone deacetylase (HDAC), an enzymethat catalyzes the remove of acetyl groups from lysine residues ofhistones, thereby altering gene expression. [Phiel C J, Zhang F, Huang EY, Guenther M G, Lazar M A, Klein P S. Histone deacetylase is a directtarget of valproic acid, a potent anticonvulsant, mood stabilizer, andteratogen. J Biol Chem 2001; 276: 36734-36741. Gottlicher M, Minucci S,Zhu P, Kramer O H, Schimpf A, Giavara S et al. Valproic acid defines anovel class of HDAC inhibitors inducing differentiation of transformedcells. EMBO J 2001; 20: 6969-6978.]

Further, potential therapeutic benefits of valproate in still otherclinical indications are being evaluated in on-going clinical trials.Valproate therapy is being evaluated in clinical studies assessingactivity of the substance as a histone deacetylase inhibitor to promotecell differentiation and regeneration, or to regulate gene expression insubjects afflicted with spinal muscular atrophy. Likewise, valproate mayexhibit therapeutic benefit as a combinatorial therapeutic treatment ofhuman cancers and for the treatment of tumor metastasis. Similarly,valproate may be useful in the treatment and management of pain, fortreating severe tinnitus, for treatment of disorders of personalattachment and deficient social interaction, or for treating Alzheimer'sdisease. Pre-clinical studies also show that valproate may promoteneural stem cell differentiation and or be useful as a co-medicament topromote the elimination of the Human Immunodeficiency Virus (HIV) orother retroviruses from the body or to prevent progression of aretroviral infection to AIDS. Clinical investigators have found thatboth lithium and valproate

Lithium is indicated for the treatment of bipolar disorder, both fortreatment of acute mania and for prophylaxis against recurrence. Otherpsychiatric conditions that may be benefited by administration oflithium include recurrent severe depressions without manic episodes,schizoaffective psychosis, episodic alcoholism, periodic antisocialbehavior, and periodic schizophrenic illness.

Sources of the Active Pharmaceutical Ingredient Valproate

Valproic acid (Chemical Abstracts Service (CAS) Registry No. 99-66-1) isa branched carboxylic acid having the molecular formula C₈H₂₆O₂.Valproic acid is also known as 2-propylpentanoic acid, 2-propylvalericacid, and dipropylacetic acid. Valproic acid is a colorless liquidhaving a boiling point of 120-121° C. at 14 torr. The compound is veryslightly soluble in water. It has a pKa of 4.6, and reacts with bases toform salts generally known as valproates.

Although valproate is a therapeutically active pharmaceuticalingredient, valproic acid is an oil that is difficult to formulate anduse in the preparation of dosage forms suitable for human or veterinaryuse. In addition, the administration of valproic acid to subjectsrequiring its therapeutic administration results in the exhibition ofdeleterious side effects, including gastrointestinal distress andulceration. Pharmaceutical and pharmacological advantages are gainedwhen therapeutic dosage forms are prepared from alkali metal or alkalineearth metal salts of valproic acid. Therefore, alkali metal or alkalineearth metal salts of valproic acid are used in present-day clinicalformulations as sources of the active drug ingredient, valproate.

Sodium (Na¹⁺), calcium (Ca²⁺) and magnesium (Mg²⁺) valproates have beenevaluated for use in pharmaceutical and veterinary compositions. Sodiumvalproate is a hygroscopic salt that is difficult to formulate intopharmaceutical formulations. In contrast, non-stoichiometric valproatesodium compounds comprising combinations of sodium valproate andvalproic acid (divalproex sodium, for example) are not hygroscopic, andare bioavailable and therapeutically active sources of valproate. (Thenon-stoichiometric compound known as divalproex sodium is disclosed inU.S. Pat. No. 4,988,731, for example, and one of its therapeuticembodiments is described in the FDA Approved Labeling Text for NDA21-168, Aug. 4, 2000.) At the present time, divalproex sodium is themost commonly formulated source of the drug valproate.

Calcium valproate has also been evaluated for use in pharmaceutical andveterinary formulations. Methods for the preparation of calcium salts ofvalproic acid are disclosed in U.S. Pat. No. 4,895,873. Althoughpharmaceutical formulations comprising calcium valproate have beenapproved by the regulatory bodies of several countries, the use of thisvalproate salt has been severely restricted following publication ofreports of adverse toxicological and reproductive effects in dogs, rats,mice, rabbits, and rats. (For example, adverse effects caused by calciumvalproate administration are reported in “Calcium valproate-induceduterine adenocarcinomas in Wistar rats” by Watkins, Gough, et al. inToxicology, Vol. 41, pages 35-47, 1993.)

Magnesium valproate is also used in clinical formulations. Magnesiumvalproate, which has the CAS Registry No. 62859-43-7, a molecularformula of C₁₆H₃₀O₄Mg, and a molecular weight of 310.71, is also knownas magnesium 2-propylvalerate and as 2-propylpentanoic acid magnesiumsalt. By weight, its composition is 61.8% carbon, 9.7% hydrogen, 7.8%magnesium, and 20.6% oxygen.

Clinical investigators have reported that magnesium valproate possessespharmacokinetic properties comparable to sodium valproate or valproicacid, is hydrolyzed to valproic acid and magnesium ions upon absorptionin the bloodstream, and has important advantages in comparison witheither sodium valproate or valproic acid. Among the therapeuticadvantages of magnesium valproate are the clinical observations thatmagnesium valproate exhibits a slower and more regular absorption rate,which prevents the variations in plasma levels of valproate typicallyobserved when sodium salts of valproic acid are administered. Additionaltherapeutic benefits are afforded by magnesium ions, which possessanticonvulsant and sedative properties. [X. Rabasseda, Drugs of Today,Vol. 31, No. 3, 1995, pp. 185-190.] In contrast to calcium valproate,which exacerbates malignancy, magnesium valproate is a useful therapywhen administered to patients with cervical cancer. For example,Chavez-Blanco et al. have reported that magnesium valproate at a dosebetween 20 and 40 mg/kg inhibits deacetylase activity andhyperacetylates histones in tumor tissues. [A. Chavez-Blanco, B.Segura-Pacheco, et al., Molecular Cancer Jul. 7, 2005, Vol. 4, pp.22ff.]

Sources of the Drug Lithium

Lithium is most frequently administered therapeutically for thetreatment of neurological dysfunction as lithium carbonate, a white,low-melting powder that is slightly soluble in water and alcohol.Lithium carbonate has a Chemical Abstracts Registry No. of 554-13-3, amolecular formula of Li₂CO₃, and a molecular weight of 73.89.

There is no commercial source of lithium valproate. No ChemicalAbstracts Registry Number has been assigned to lithium valproate. Itsphysico-chemical properties have not been reported.

Polytherapy with Lithium and Valproate

Recently there has been a great deal of interest in the use ofcombinations of therapeutic agents, i.e., “polytherapies,” in thetreatment of neurological disorders. In routine practice for acutemania, both lithium and valproate, administered as separate entities,are useful as adjuncts to antipsychotic drugs, rather than asmonotherapy. The antipsychotic activity of valproate is exhibitedrelatively quickly after therapeutic doses are administered. Incontrast, lithium has a delayed effect, taking a few days to begin, and2-8 weeks or longer to approach its full effect on mania.

Lambert and other French investigators have reported beneficialtherapeutic responses to the concomitant administration of valproate(administered as valpromide) and lithium for the treatment of patientswith major affective disorders and schizophrenia. [P. A. Lambert. Acuteand prophylactic therapies of patients with affective disorders usingdipropylacetamide or valpromide. Proceedings of the 7^(th) WorldCongress of Psychiatry, Vienna, Jul. 11-16, 1983. G. W. Semadeni. Etudeclinique de I'effet normothymique du di-propylacetamide. Acta PsychiatrBelg 1976; 76: 458-466.] That response permitted a reduction in thedosage levels of the psychotropic agent required to maintain optimalimprovement, which in turn reduced the overall risk of adverseexperiences. Further, long-term administration of combinations ofvalproate and lithium suggested that these two agents may exert asynergistic effect in bipolar patients that is particularly useful inpatients whose symptoms are inadequately controlled by lithium alone.Moreover, the adverse effects observed with the concomitantlyadministered combination were typically only those noted with the use ofeither individual agent. No unique adverse effects occurring as a resultof the drug combination were reported.

Hayes has completed a retrospective study of clinical cases in whichvalproate [as Depakote® (sodium hydrogen divalproate; AbbottLaboratories, Inc., McGaw Park, Ill.] or combinations of valproate andlithium were administered to 35 patients, all with major depressiveillness, bipolar disorder, or schizoaffective disorder, wereretrospectively identified as having received valproate either alone orin combination with lithium, after having failed to respond adequatelyto previous lithium and/or carbamazepine treatment. [S. G. Hayes, M. D.Long-term valproate use in psychiatric disorders. J. Clin Psychiatry 50(3, Suppl), pages 35-39.] Clinical evaluation and Global AssessmentScale (GAS) scores indicated that at baseline all but 3 of the patientsexperienced serious psychiatric symptoms, serious impairment in socialor professional functioning, or significant impairment in realitytesting. Mean GAS scores after a mean duration of at least 1 year ofvalproate administration improved in 7 of 9 depressed patients, 12 of 12patients with bipolar disorder, and 11 of 14 patients withschizoaffective states. For patients with either depressive disorders ormixed bipolar disorders, that mean change represented a level ofimprovement sufficient to elevate the majority of the patients into themild symptom range or the virtually asymptomatic state. Patients withbipolar and schizoaffective disorders to valproate treatment compared tovalproate plus lithium were evaluated for an average of 11 to 14 monthsof treatment. Patients in both treatment groups demonstrated verysimilar and quite substantial improvement in mean change in GAS ratings(35.0 and 33.8, respectively, for the valproate and valproate+lithiumgroups) and global evaluations, regardless of whether valproate wasadministered alone or in combination with lithium. As an anecdotalobservation, certain patients did respond better to the combination ofvalproate and lithium, although this response did not happen frequentlyenough to reach statistical significance.

Over the past two decades, clinicians increasingly have used concomitantadministration of a lithium drug and valproate, optionally with a thirddrug, to beneficially mitigate the mania and depression associated withBPD. For example, Sharma et al. reported treatment of rapid cycling BPDwith combination therapy of valproate and lithium. [V. Sharma, E.Persad, D. Mazmanian, K. Karunaratne. Treatment of rapid cycling bipolardisorder with combination therapy of valproate and lithium. Can. J.Psychiatry 1993; 38: 137-139.]

In U.S. Patent Application 2005/0233010 Salow discloses combinatorialtherapies for treating anxiety, depression or psychotic conditions usinga co-therapy regimen comprising a lithium salt and a psychoactive drugselected from the group consisting of serotonin reuptake inhibitor, a5HT₂ receptor antagonist, an anticonvulsant, a norepinephrine reuptakeinhibitor, an α-adrenoreceptor antagonist, an NK-3 antagonist, an NK-1receptor antagonist, a PDE4 inhibitor, a neuropeptide Y5 ReceptorAntagonist, a D4 receptor antagonist, a 5HT_(1A) receptor antagonist, a5HT_(1D) receptor antagonist, a CRF antagonist, a monoamine oxidaseinhibitor, a sedative-hypnotic drug, and an atypical psychotic.Exemplary forms of lithium salts include lithium carbonate, lithiumcitrate, lithium acetate, lithium glutamate, lithium orotate, lithiumthionate, and lithium sulphate. Valproate is named as an anticonvulsantdrug that may be co-administered with a lithium salt.

Lithium valproate has not, however, been available for clinical use. Inthe absence of lithium valproate, clinicians and patients have noted thefollowing serious difficulties in treatment management. Concomitantadministration of lithium with other antipsychotic drug(s) canunexpectedly increase intracellular lithium levels, a possible mechanismfor unanticipated adverse interactions and resulting toxicity. Patientswith bipolar disorder demonstrate poor compliance with dosing regimensthat included two different drugs (i.e., a lithium drug and a valproatedrug) and/or two different dosing regimens and suffer the occurrence ofwithdrawal mania. Poor compliance with the aforementioned dosingregimens also increases the risks of side effects and toxicity,including the possibility of permanent neurological sequelae withcerebellar damage. (Valproate toxicity includes dizziness; elevatedSGPT, SGOT, alkaline phosphatases, and LDH values; and sedation and/ornausea. Lithium toxicity includes the potential for extrapyramidalside-effects, cogwheel rigidity, cerebellar tremor, incoordination,severe neurological symptoms, hyperthermia, impaired consciousness andirreversible brain damage.) [J. C. Cookson. The neuroendocrinology ofmania. J Affect Disorders 1985; 8:233-241. M. Schou. Long-lastingneurological sequelae after lithium intoxication. Acta Psych. Scand.1984; 70: 594-602.]

Among the drugs that have been studied as potential treatments for HADare antioxidant medications, calcium channel antagonists, NMDAantagonists, platelet activating factor inhibitors, and drugs thatinhibit glycogen synthase kinase 3 beta (GSK-3β) and mixed lineagekinase (MLK). Specifically, sodium valproate and lithium ion, existingepilepsy drugs, have proven to be GSK-3β inhibitors having strongpotential as treatments for HAD. Schifitto et al., for example,conducted a pilot 10-week placebo-controlled study of valproate (250 mgtwice daily) in 22 HIV-infected individuals with (n=16) and without(n=6) cognitive impairment. [G. Schifitto, D. R. Peterson, J. Zhong, H.Ni, K. Cruttenden, M. Gaugh, H. E. Gendelman, M. Boska, and H. Gelbard.Valproic acid adjunctive therapy for HIV-associated cognitiveimpairment. A first report. Neurology 2006.) Valproate was safe and welltolerated, with trends toward improved neuropsychological performanceand brain metabolism in the impaired subjects.

In brief, clinicians have shown that both lithium (ion) and valproateare useful drugs for the treatment of neurological disorders. To date,however, the lack of availability of lithium valproate as a stable,non-hygroscopic valproate salt has prevented broader therapeuticapplications of lithium valproate. The present invention remedies theseshortcomings.

GENERAL DESCRIPTION OF THE INVENTION

Conventionally, combinations of lithium salts and valproate salts,administered independently, are used for the treatment of bipolardisorder and other neurological disorders, and are being evaluated ascombination therapies for the treatment of immunological disorders andviral-related disorders. The present invention provides a heretoforeunknown valproate salt, lithium valproate, together with methods for itspreparation, formulation into pharmaceutical dosage forms, andtherapeutic uses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the ¹H-Nuclear Magnetic Resonance (¹H-NMR) spectrum ofvalproic acid in perdeutero-methanol solution.

FIG. 2 is the ¹H-NMR spectrum of lithium valproate inperdeutero-methanol solution.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides lithium valproate, a heretofore unknownvalproate salt. A CAS Registry Number has not yet been assigned to thissubstance. The molecular formula of lithium valproate is C₈H₁₅O₂Li. Byweight, its composition is 59.4% carbon, 9.8% hydrogen, 7.5% lithium,and 23.3% oxygen. Lithium valproate is about 4.6% lithium and 95.4%valproate by weight. Also within the scope of this invention are lithiumvalproate compositions having specific bulk densities or tap densities,and lithium valproate compositions having specific particle sizes.Further included within the scope of this invention are lithiumvalproate compositions coated with pharmaceutically acceptable materialsintended to modify the release and/or bioavailability of the lithiumvalproate (e.g., Eudragit, microcrystalline cellulose,hydroxypropylmethylcellulose phthalate, and so forth).

The present invention relates to methods for preparing lithium valproateas a stable, non-hygroscopic solid that is suitable for pharmaceuticalformulation and therapeutic use. Lithium valproate is a bioavailablesource of both lithium ion and valproate, each of which is a drug thatis useful for several clinical indications, including neurologicaldisorders, including mania, manic episodes associated with bipolardisorder, epilepsy, and affective and attention deficit disorders. Inaddition, valproate is used for the prophylactic treatment, modulationand management of migraine headache, chronic pain, and neuropathic pain.Further, lithium is used for the treatment of bipolar disorder, both fortreatment of acute mania and for prophylaxis against recurrence. Otherpsychiatric conditions that may be benefited by administration oflithium include recurrent severe depressions without manic episodes,schizoaffective psychosis, episodic alcoholism, periodic antisocialbehavior, and periodic schizophrenic illness. Combinations of lithiumsalts and valproate salts, administered independently, are used for thetreatment of bipolar disorder and other neurological disorders, and arebeing evaluated as combination therapies for the treatment ofimmunological disorders and viral-related disorders.

The present invention also relates to a method of formulating lithiumvalproate in solid dosage forms or in water or aqueous solutions inconcentrations that provide a therapeutically effective amount oflithium and/or valproate to a warm-blooded animal after the formulationis administered to the animal.

According to the methods of the present invention, lithium valproate isadministered, alone or in combination with other therapeutically activeor inactive substances, as a therapeutically effective and biologicallyavailable (i.e., bioavailable) source of lithium (ion) and valproatethat are useful for the treatment of neurological, immunological, andviral-related disorders. Therapeutically effective concentrations oflithium valproate are a useful treatment and prophylaxis againstrecurrence for neurological disorders, including mania, manic episodesassociated with bipolar disorder, epilepsy, and affective and attentiondeficit disorders; for the prophylactic treatment, modulation andmanagement of migraine headache, chronic pain, and neuropathic pain; forthe treatment of bipolar disorder, both for treatment of acute mania andfor prophylaxis against recurrence; for the treatment of recurrentsevere depressions without manic episodes, schizoaffective psychosis,episodic alcoholism, periodic antisocial behavior, and periodicschizophrenic illness; and for the treatment of immunological disordersand viral-related disorders, including HIV-related dementia.

The term “alkoxide of a lower alcohol” as used herein means the oxyanion of an alcohol having from 1 to 6 carbons, arranged linearly orbranched. Preferred alkoxides of the present invention are methoxide,ethoxide, propoxide, isopropoxide, butoxide, and t-butoxide.

The term “excipient material” means any compound forming a part of theformulation, which is not intended to have independent biologicalactivity, and which is added to a formulation to provide specificcharacteristics to the dosage form, including providing protection tothe active ingredient from chemical degradation (for example, a polymercoating such as hydroxypropyl methylcellulose or Eudragit, or ananti-oxidant such as L-cysteine HCl or sodium metabisulfite),facilitating release of a tablet or caplet from the contact surfaces ofmanufacturing equipment (for example, magnesium stearate), and so forth.

By the terms “treating” and “treatment” and the like are used herein togenerally mean obtaining a desired pharmacological and physiologicaleffect. The effect may be prophylactic in terms of preventing orpartially preventing a disease, symptom or condition thereof and/or maybe therapeutic in terms of a partial or complete cure of a disease,condition, symptom or adverse effect attributed to the disease. The term“treatment” as used herein encompasses any treatment of a disease in amammal, particularly a human and includes: (a) preventing the diseasefrom occurring in a subject which may be predisposed to the disease buthas not yet been diagnosed as having it; (b) inhibiting the disease orarresting its development; (c) relieving the disease, causing regressionof the disease and/or its symptoms or conditions; or (d) returning aclinical value to the concentration range normally found in a subject.

The phrase “therapeutically effective” is intended to qualify the amountof lithium valproate for use in the orally or intravenously administeredtherapy which will achieve the goal of providing a biologicallyavailable (i.e., bioavailable) concentration of the drugs lithium andvalproate to effect reducing or preventing, for example, a neurological,immunological, or viral-related disorder, while avoiding adverse sideeffects typically associated with valproic acid, sodium valproatecompositions, or other valproate salts.

Included within the scope of this invention is a method of treatingneurological disorders, immune disorders, or viral-related disorders ina warm-blooded animal using pharmaceutical compositions comprisinglithium valproate and a suitable pharmaceutical carrier. Also includedwithin the scope of this invention is a method of treating neurologicaldisorders, immune disorders, or viral-related disorders in awarm-blooded animal using pharmaceutical compositions comprising lithiumvalproate and a suitable pharmaceutical carrier, or pharmaceuticalcompositions comprising lithium valproate, a linear or branched alcoholhaving from 1 to about 6 carbon atoms, or an organic polyol having from2 to 100 hydroxyl groups, and a suitable pharmaceutical carrier.

For the purpose of this disclosure, a warm-blooded animal is a member ofthe animal kingdom which includes but is not limited to mammals andbirds. The most preferred mammal of this invention is human.

Surprisingly, the inventors have discovered methods for the preparationof a heretofore unknown valproate salt, lithium valproate, which affordsignificant advantages, particularly in pharmaceutical manufacturing andformulation. Thus, lithium valproate of the present invention, a whitesolid, is recovered in high yields from reactions of valproic acid and alithium alkoxide in solutions of a lower alcohol and a hydrocarbonsolvent.

Even more surprisingly, the inventors have discovered that lithiumvalproate is recovered in high yields from reactions of valproic acidand a lithium alkoxide in a hydrocarbon solvent. Preferably, the lithiumalkoxide is lithium t-butoxide and the hydrocarbon solvent is hexane.

The lithium valproate solid thus obtained has high purity, is free ofcontaminating inorganic and organic lithium salts and residual solvents,is not hygroscopic or deliquescent, and is stable during storage.Further, the lithium valproate of the present invention readilydissolves in water or aqueous solutions to provide aqueous solutionshaving a lithium concentration in the range from about 0.04 mg/mL toabout 10 mg/mL and a valproate concentration in the range from about 1mg/mL to about 250 mg/mL and near neutral pH.

Lithium valproate of the present invention is a white solid having themolecular formula C₈H₁₅O₂Li. By weight, its composition is 63.99%carbon, 10.07% hydrogen, 4.62% lithium, and 21.32% oxygen. Lithiumvalproate is about 4.6% lithium and 95.4% valproate by weight.

A conventional method for the preparation of an alkali metal salt of anorganic acid is by reacting a metal oxide, metal bicarbonate, metalcarbonate, or metal hydroxide with a carboxylic acid in a lower alcoholsolution, as disclosed, by way of example, by Trusovs in U.S. Pat. No.6,670,494. Attempts to prepare lithium valproate by this conventionalapproach failed to provide lithium valproate solid of the presentinvention. Reaction of lithium hydroxide with valproic acid in ethanol,for example, provided an intractable, brown oil that failed tocrystallize. When lithium carbonate was substituted for lithiumhydroxide in the reaction, the ethanol solution never became clear, andit was difficult to monitor the progress of the reaction and isolate thedesired product, lithium valproate, from residual lithium carbonatesalts.

After extensive experimentation, we discovered that reaction of valproicacid with a lithium alkoxide in alcohol solution provided, afteraddition of a low-boiling hydrocarbon (such as petroleum ether, pentane,hexane, heptane, octane, benzene, toluene, or xylene, for example),lithium valproate as a white solid that was stable and non-hygroscopic.Further, we discovered to our surprise that the reaction could besimplified by carrying out the synthesis in a low-boiling hydrocarbon byreacting valproic acid and a molar equivalent of lithium alkoxide in thehydrocarbon. Under these conditions, lithium valproate precipitated andwas isolated by filtration. Conveniently, a solution of lithiumt-butoxide in hexane is commercially available, but solutions of otherlithium alkoxides in other hydrocarbons are also useful in this methodof preparation and are prepared by reaction of lithium metal with analcohol in a hydrocarbon solvent.

The methods for the preparation of lithium valproate that are disclosedherein are advantageously useful in pharmaceutical manufacturing of thisvalproate salt, as illustrated by way of example, by the following. Theraw materials and solvents are commercially available. The reactionconditions enable control of reaction temperature, monitoring of theprogress of reaction for extent of completion, methods for the removalof impurities, and convenient and high yield steps for the recovery oflithium valproate from the solution.

The lithium valproate obtained by the methods of the present inventionexhibits both high purity and absence of both solvents and chemical andbiological contaminants, qualities qualifying it for use inpharmaceutical formulations. The lithium valproate of the presentinvention is a white solid that is not hygroscopic or deliquescent andis stable during storage. Further, this valproate salt is easily milledor processed into formulary dosage forms using conventional methods andtechniques.

In general, the solubilities of lithium salts of organic acids in wateror aqueous solutions vary unpredictably. Lithium carbonate, for example,is slightly soluble in water and insoluble in ethyl alcohol. Lithiumacetate is soluble in water and ethyl alcohol. Lithium citrate issoluble in water and slightly soluble in ethyl alcohol. Surprisingly,the inventors have found that formulations of lithium valproate inaqueous solution are readily prepared by dissolving lithium valproate ofthe present invention in water or aqueous solutions containing ethylalcohol or a polyol, such as propylene glycol, polyethylene glycol,mannitol, xylitol, or dextrose. In this manner, clear and colorlessaqueous solutions of lithium valproate are reproducibly obtained,wherein the concentrations of lithium and valproate in solution are inthe range from about 0.04 mg/mL to 10 mg/mL lithium and from about 1mg/mL to about 250 mg/mL valproate, respectively.

The availability of lithium valproate of the present invention as apharmaceutical quality compound of known composition and exhibitingthermal stability and an absence of hygroscopicity is particularlyimportant for pharmaceutical and therapeutic applications of lithiumvalproate. Lithium valproate as provided herein may be formulated toprovide known concentrations of lithium and valproate. In this manner,dosage forms having known quantities of lithium valproate can beprepared for administration to a subject by any of a variety of routes,including oral, parenteral, and inhalation. The inventors expect thatthe concomitant provision of lithium and valproate as lithium valproateof the present invention will be particularly useful in the treatment ofchildren or small adults having neurological or viral disorders.

Lithium valproate of the present invention affords significantadvantages in treatment management to both clinicians and patients.Since lithium valproate of the present invention provides both lithiumion and valproate in known concentrations, a requirement for theseparate but concomitant administration of both a lithium drug and avalproate drug is eliminated. Patients with bipolar disorderdemonstrated poor compliance with dosing regimens that included twodifferent drugs (i.e., a lithium drug and a valproate drug) and sufferedthe occurrence of withdrawal mania. Poor compliance with theaforementioned dosing regimens also increased the risks of side effectsand toxicity, including the possibility of permanent neurologicalsequelae with cerebellar damage. Concomitant administration ofconventional lithium salts with other antipsychotic drug(s) canunexpectedly increase intracellular lithium levels, a possible mechanismfor unanticipated adverse interactions and resulting toxicity. Lithiumvalproate of the present invention provides known quantities of lithiumand valproate and is expected to prevent these unexpected increases.

Dosage Forms. The pharmaceutical compositions of this invention can beadministered by any means that effects contact of the active ingredientswith the site of action in the body of a warm-blooded animal. Forexample, the means can be oral, transdermal, by inhalation, orparenteral (i.e., subcutaneous, intravenous, intramuscular orintraperitoneal). Alternatively or concurrently, the means ofadministration can be by more than one route (e.g., oral andparenteral). A most preferred means of administration is by the oralroute (i.e., ingestion).

The active ingredients can be administered by the oral route in soliddosage forms, such as tablets, capsules, and powders, or in liquiddosage forms, such as elixirs, syrups, and suspensions. Thepharmaceutical compositions of this invention also can be administeredparenterally, in sterile liquid dosage forms. The pharmaceuticalcomposition is preferably made in the form of a dosage unit containing aparticular amount of each active ingredient.

In general, the pharmaceutical compositions of this invention can beprepared by conventional techniques, as are described in Remington'sPharmaceutical Sciences, a standard reference in this field [Gennaro AR, Ed. Remington: The Science and Practice of Pharmacy. 20^(th) Edition.Baltimore: Lippincott, Williams & Williams, 2000]. For therapeuticpurposes, the active components of this combination therapy inventionare ordinarily combined with one or more adjuvants appropriate to theindicated route of administration. If administered per os, thecomponents may be admixed with lactose, sucrose, starch powder,cellulose esters of alkanoic acids, cellulose alkyl esters, talc,stearic acid, magnesium stearate, magnesium oxide, sodium and calciumsalts of phosphoric and sulfuric acids, gelatin, acacia gum, sodiumalginate, polyvinylpyrrolidone, and/or polyvinyl alcohol, and thentabletted or encapsulated for convenient administration. Such capsulesor tablets may contain a controlled-release formulation as may beprovided in a dispersion of active compound in hydroxypropylmethylcellulose. Solid dosage forms can be manufactured as sustainedrelease products to provide for continuous release of medication over aperiod of hours. Compressed tablets can be sugar coated or film coatedto mask any unpleasant taste and protect the tablet from the atmosphere,or enteric coated for selective disintegration in the gastrointestinaltract. Both the solid and liquid oral dosage forms can contain coloringand flavoring to increase patient acceptance.

Formulations for parenteral administration may be in the form of aqueousor non-aqueous isotonic sterile injection solutions or suspensions.These solutions and suspensions may be prepared from sterile powders orgranules having one or more of the carriers or diluents mentioned foruse in the formulations for oral administration. The components may bedissolved in water, polyethylene glycol, propylene glycol, ethanol, cornoil, cottonseed oil, peanut oil, sesame oil, benzyl alcohol, sodiumchloride, and/or various buffers. The indicated formulations can containcompatible auxiliaries and excipients, such as anti-oxidants,preservatives, stabilizing agents, emulsifiers, salts for influencingthe osmotic pressure, and/or buffer substances.

Other adjuvants and modes of administration are well and widely known inthe pharmaceutical art.

Pharmaceutical compositions for use in the treatment methods of theinvention may be administered in oral form or by intravenousadministration. Oral administration of the therapy is preferred. Dosingfor oral administration may be with a regimen calling for single dailydose, or for a single dose every other day, or for multiple, spaceddoses throughout the day. The active agents which make up the therapymay be administered simultaneously, either in a combined dosage form orin separate dosage forms intended for substantially simultaneous oraladministration. The active agents which make up the therapy may also beadministered sequentially, with either active component beingadministered by a regimen calling for two-step ingestion. Thus, aregimen may call for sequential administration of the active agents withspaced-apart ingestion of the separate, active agents. The time periodbetween the multiple ingestion steps may range from a few minutes toseveral hours, depending upon the properties of each active agent such apotency, solubility, bioavailability, plasma half-life and kineticprofile of the agent, as well as depending upon the age and condition ofthe patient. The active agents of the therapy whether administeredsimultaneously, substantially simultaneously, or sequentially, mayinvolve a regimen calling for administration of one active agent by oralroute and the other active agent by intravenous route. Whether theactive agents of the therapy are administered by oral or intravenousroute, separately or together, each such active agent will be containedin a suitable pharmaceutical formulation of pharmaceutically-acceptableexcipients, diluents or other formulations components.

Clinical Uses of Lithium Valproate

The present invention provides methods for the reproducible preparationof pharmaceutical quality lithium valproate as well as methods for itsformulation into pharmaceutical dosage forms using conventionalpharmaceutical techniques. In addition, the inventors have shown thataqueous solutions of lithium valproate are readily prepared to havelithium concentrations in the range from about 0.4 mg/mL to about 12.5mg/mL and and valproate concentrations from about 1 mg/mL to about 250mg/mL. Aqueous solutions of lithium valproate comprise fully ionizedsolutions of lithium ions and valproate ions which, after parenteraladministration to a subject, are completely bioavailable. The inventorshave also shown that lithium valproate is soluble in simulated gastricfluid USP and in simulated intestinal fluid USP. Given this solubility,the inventors expect that lithium valproate, when administered per os toa subject, will exhibit a bioavailability at least about 90% relative tointravenous infusion, a bioavailability that is equivalent to or exceedsthat of divalproex sodium. On these bases, therefore, the inventorsexpect that lithium valproate of the present invention will beadministered to subjects in need of valproate therapy as atherapeutically effective and biologically available substitute forvalproic acid, divalproex sodium, valproate sodium, and other valproatesalt compositions.

For example, the inventors expect that lithium valproate of the presentinvention will be substituted for valproic acid, divalproex sodium,valproate sodium and other valproate salt compositions in compositionsuseful for the treatment of neurological disorders as disclosed, by wayof example, in U.S. Patent Applications 20050095579, 20050090548,20050090449, 20050075282, 20050070524, and 20050065340, as well as inU.S. Pat. Nos. 6,406,716, 6,323,236, 6,287,598, and 5,945,416 and ininternational patents EP 1371366 A1, EP 0966967 A3, EP 1158973 B1, WO2005070461, WO 2005063297, WO 2005051915, WO 2005049040, and WO2004101603. Further, the inventors expect that lithium valproate of thepresent invention will be substituted for valproic acid, divalproexsodium, valproate sodium and other valproate salt compositions incompositions useful for the treatment of immunological disorders asdisclosed, by way of example, in U.S. Patent Applications 20050119261,20050090553, 20050065596, 20050065173, 20050054091, as well as in U.S.Pat. Nos. 5,506,224 and 5,432,176 and in international patents EP1529527 A1, EP 1293205 A1, EP 1170008 A1, EP 1301184 B1, WO 2005023179,WO 2005018578, WO 2004113305, WO 2004096216, WO 2004096224, and WO2004050076. Likewise, the inventors expect that lithium valproate of thepresent invention will be substituted for valproic acid, divalproexsodium, valproate sodium and other valproate salt compositions incompositions useful for the treatment of viral-related disorders asdisclosed, by way of example, in the report of Smith [Retrovirology Sep.19, 2005, 2(1): 56], Cohen [Science Aug. 12, 2005, 309(5737): 999-1000],Lehrman et al. [Lancet Aug. 13, 2005, 366(9485): 549-555], andYlisastigui et al. [AIDS May 21, 2004, 18(8): 1101-1108].

The inventors expect that lithium valproate of the present inventionwill have particular therapeutically beneficial when administered to awarm-blood mammal for the treatment of neurological disorders, includingbipolar disorders and HIV-associated dementia.

The inventors further expect that the pharmacokinetics of particularlyfavorable embodiments of lithium valproate of the present inventionallow for administration of total daily doses of lithium as small as 25mg/day, 30 mg/day, 40 mg/day, or 50 mg/day, or lower. In other words,lithium valproate of the present invention will, we expect, be usefulfor administration of doses of lithium and valproate which may be ofparticular benefit for children or individuals of small stature andweight.

The following examples present representative compositions of thepresent invention. The examples are representative of the scope of theinvention, and as such are not to be considered or construed as limitingthe invention recited in the appended claims.

EXAMPLE 1

Attempted preparation of lithium valproate. A conventional method forthe preparation of salts of organic acids is by reaction of a metalhydroxide or carbonate with an organic acid. Valproic acid (2 g, 0.0138mol) was dissolved in 40 mL of ethanol, and a slurry of lithiumhydroxide (0.56 g, 0.0138 mol) in 10 mL of ethanol was added. Theresulting reaction mixture was stirred at room temperature for 3 hours.The color of the solution changed from colorless to brown during thistime. Stirring was continued for an additional hour, and then thereaction mixture was filtered to remove residual solids (0.17 g). Thefiltrate was concentrated under vacuum to a residual oil. Even aftertrituration with organic solvents, the oil did not crystallize orprovide a solid of known composition. The reaction failed to providelithium valproate solid.

EXAMPLE 2

Preparation of lithium valproate of the present invention. Valproic acid(2.7 g, 0.018 mol) was dissolved in 25 mL of ethanol to provide a clear,colorless solution. One equivalent of lithium t-butoxide (as a 1 Msolution in hexane) was added dropwise. At the completion of theaddition, a white solid formed, and 15 mL of hexane was added tofacilitate stirring. Stirring was continued for an hour, and 25 mL ofhexane was added. The solid was isolated by filtration and dried toconstant mass (1.7 g, 63% of theoretical). Additional product (0.4 g,14% of theoretical) was obtained by concentration of the filtrate undervacuum and cooling. The product, lithium valproate, was a white solidthat did not melt at a temperature less than 300° C. (the highesttemperature tested). The product was very soluble in water and methanol.The ¹H-NMR spectrum of a perdeutero-methanol solution of the product(FIG. 2) differed from that of valproic acid (FIG. 1) and confirmed thatthe product was a valproate salt. (Lithium is not detected by ¹H-NMR.)

EXAMPLE 3

Preparation of lithium valproate of the present invention. Valproic acid(2.7 g, 0.018 mol) was dissolved in 25 mL of hexane to provide a clear,colorless solution. One equivalent of lithium t-butoxide (as a 1 Msolution in hexane) was added dropwise. At the completion of theaddition, a white solid formed. Stirring was continued for an hour. Thesolid 10 was isolated by filtration and dried to constant mass (2.4 g,85% of theoretical). Additional product (0.4 g, 14% of theoretical) wasobtained by concentration of the filtrate under vacuum and cooling. Theproduct, lithium valproate, was a white solid that did not melt at atemperature less than 300° C. (the highest temperature tested). Theproduct was very soluble in water and methanol. The ¹H-NMR spectrum oflithium valproate (FIG. 2) differed from that of valproic acid (FIG. 1)and confirmed that the product was a valproate salt. (Lithium is notdetected by ¹H-NMR.)

EXAMPLE 4

Valproate analysis by HPLC. Weight percent valproate was determined byreversed-phase HPLC analysis using the following conditions:

-   -   Column: X-Terra Reversed-Phase C18, 5 μM particle size, 4.6 mm        i.d.×250 cm length (Waters)    -   Mobile Phase A: Acetonitrile (ACN):Water:Trifluoroacetic acid        (TFA) 10:90:0.1 (v/v/v)    -   Mobile Phase B: ACN:TFA 100:0.1 (v/v)    -   Separation Conditions: Isocratic delivery of A and B in a 60:40        volume ratio of A:B    -   Flow Rate: 1.0 mL/min    -   Detection Wavelength: 210 nm    -   Sample Diluent: Water containing 0.1% TFA    -   Injection Volume: 5.0 μL    -   Valproate Retention Time: 9.3 minutes    -   Acquisition Time: 12 minutes        Valproate standards with concentrations ranging from 0.05 μg/mL        to 0.5 μg/mL were prepared by dissolution of aliquots of        valproic acid and analyzed in triplicate to provide a standard        curve, which exhibited a linearity, R, of 0.99998. Peak tailing        of the valproate response was less than 2.0. Test samples were        prepared by accurately weighing approximately 40 mg of sample,        quantitatively transferring the solid to a 100-mL volumetric        flask and diluting with water containing 0.1% TFA. Sample        analyses were completed in triplicate. Relative standard error        of analysis was 1% or less. Sample analyses confirmed the        presence of valproate.

EXAMPLE 5

Preparation of Aqueous Solutions of Lithium Valproate. Aqueous solutionsof lithium valproate were prepared in the following manner. Portions oflithium valproate of the present invention were added to 1 mL of waterand stirred to effect dissolution. Addition continued until an addedportion of lithium valproate failed to dissolve. The solubility oflithium valproate was determined as about 250 mg of lithium valproateper mL of water.

EXAMPLE 6

Lithium and valproate, independently administered, in the treatment ofprimary psychiatric disorders. The study summarized below was reportedby Stephen G. Hayes, M.D., in Journal of Clinical Psychiatry 50 (3,Suppl), pages 35-39. Thirty-five patients, all with major depressiveillness, bipolar disorder, or schizoaffective disorder, wereretrospectively identified as having received valproate either alone orin combination with lithium, after having failed to respond adequatelyto previous lithium and/or carbamazepine treatment. Clinical evaluationand Global Assessment Scale (GAS) scores indicated that at baseline allbut 3 of the patients experienced serious psychiatric symptoms, seriousimpairment in social or professional functioning, or significantimpairment in reality testing. Mean GAS scores after a mean duration ofat least 1 year of valproate administration improved in 7 of 9 depressedpatients, 12 of 12 patients with bipolar disorder, and 11 of 14 patientswith schizoaffective states. For patients with either depressivedisorders or mixed bipolar disorders, that mean change represented alevel of improvement sufficient to elevate the majority of the patientsinto the mild symptom range or the virtually asymptomatic state. Theresponses of patients with bipolar and schizoaffective disorders tovalproate treatment compared to valproate plus lithium treatment werealso evaluated. Patients in both diagnostic categories demonstrated verysimilar and quite substantial improvement in mean change in GAS ratingsand global evaluations, regardless of whether valproate was administeredalone or in combination with lithium.

The following example presents a hypothetically useful therapeutic useof representative pharmaceutical compositions of the present inventionand the anticipated outcomes in treating neurological diseases insubjects requiring such treatment. The example is representative of thescope of the invention, and as such is not to be considered or construedas limiting the invention recited in the appended claims.

EXAMPLE 7

Lithium valproate of the present invention in the treatment of primarypsychiatric disorders. A study is completed that is similar to the onereported by Stephen G. Hayes, M.D., in Journal of Clinical Psychiatry 50(3, Suppl), pages 35-39. Thirty-five patients, all with major depressiveillness, bipolar disorder, or schizoaffective disorder, will beidentified as having received valproate either alone or in combinationwith lithium, after having failed to respond adequately to previouslithium and/or carbamazepine treatment. Clinical evaluation and GlobalAssessment Scale (GAS) scores will be completed and will indicate thatat baseline more than 90% of the patients experience serious psychiatricsymptoms, serious impairment in social or professional functioning, orsignificant impairment in reality testing. After a mean duration of atleast 1 year of lithium valproate administration, the following resultsare expected. Mean GAS scores improve in at least about 60% of depressedpatients, at least about 90% of patients with bipolar disorder, and atleast about 75% of patients with schizoaffective states. For patientswith either depressive disorders or mixed bipolar disorders, that meanchange is expected to represent a level of improvement sufficient toelevate the majority of the patients into the mild symptom range or thevirtually asymptomatic state.

All mentioned references are incorporated by reference as if herewritten. When introducing elements of the present invention or thepreferred embodiment(s) thereof, the articles “a”, “an”, “the” and“said” are intended to mean that there are one or more of the elements.The terms “comprising”, “including” and “having” are intended to beinclusive and mean that there may be additional elements other than thelisted elements.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The specific embodiments are, therefore, to beconstrued as merely illustrative, and not limitative of the remainder ofthe disclosure in any way whatsoever.

1. Lithium valproate of high purity suitable for pharmaceuticalformulation consisting essentially of a non-hygroscopic white solidhaving the molecular formula C₈H₁₅O₂Li, stable at temperatures less than300 degrees C., and having an NMR spectrum consistent with the moiety

made by the method of adding a lithium alkoxide to valproic acid in ahydrocarbon solution, and recovering the lithium valproate therefrom byfiltration.
 2. Lithium valproate of high purity suitable forpharmaceutical formulation consisting essentially of a non-hygroscopicwhite solid having the molecular formula C₈H₁₅O₂Li, stable attemperatures less than 300 degrees C., and having an NMR spectrumconsistent with the moiety